Practical Access to 2-Alkylsuccinates through Asymmetric Catalytic Hydrogenation of Stobbe-Derived Itaconates

Enantiomerically pure 2-alkylsuccinates are obtained on a 500-g scale after hydrogenation with the cationic rhodium complexes with tetraalkyl-substituted 1,2-bis(phospholanyl)ethane or -benzene ligands [R′-DuPHOS; Eq. (a)]. The catalysts allow smooth hydrogenation of mixtures of the prochiral E and Z isomers of itaconate derivatives with very high enantioselectivities and catalytic efficiencies; even tetrasubstituted itaconates were hydrogenated with 96% ee.